In recent years, optical access systems have used optical communication systems each of which accommodate a plurality of subscribers with a passive double star configuration, such as Ethernet-PON (E-PON) and Gigabit capable-PON (G-PON). Some of the optical communication systems may have a transmission capacity in the range of 1 Gbps (hereinafter, will be simply written as “G”), for example.
The application of a communication system having a transmission capacity of 10G has been considered for next generation PON systems in order to increase the transmission rate. For longer distances and more branches in order to expand a service range, the addition of a repeater has also been examined.
A PON system that is acceptable to mixed systems having different transmission rates may be assumed for an economically and efficiently improved transmission rate. For example, the network system may correspond to a mixed system including both 1G system and 10G system. In such a network system, the integration of a repeater may be assumed for longer transmission distance.
Those technologies may be disclosed in Japanese Laid-open Patent Publication Nos. 2008-17264 and 2002-141927.